This invention is in the field of plant molecular biology. More specifically, this invention pertains to nucleic acid fragments encoding factors involved in regulation of transcription and gene expression in plants and seeds.
Factors involved in the control of gene expression are important throughout plant development. Anti-silencing function genes have been described for the budding yeast Saccharomyces cerevisiae. Overexpression of anti-silencing function genes leads to derepression of the silent mating type loci. At least two genes encode anti-silencing proteins which in yeast have been ascribed the designation ASF1 and ASF2, for anti-silencing function 1 and 2, respectively. Anti-silencing function genes are transcribed in a cell-cycle-specific manner and at least one of them is suggested to play a role in DNA repair and chromosome maintenance (Davis, L. S., Konopka, J. B. and Sternglanz, R. (1997) Yeast 13:1029-1042). There is no prior description of these functions or their genes in plants.
The fate of plant cells is position dependent and maintained through interactions between neighboring cells. Polycomb-group genes are involved in the maintenance of fate in Drosophila melanogaster. (Paro, R. (1990) Trends Genet. 6:416-421). Polycomb group-like proteins have been identified in Arabidopsis thaliana where they have been shown to be necessary for the stable repression of a floral homeotic gene and to promote fate determination (Goodrich, J. et al. (1997) Nature 386:44-51; Weigel D. (1997) Curr. Biol. 7:R373-R375). While a family of polycomb-like proteins have been identified in insects and animals, not all of the different classes have been identified in plants. Polycomb group proteins are thought to assemble in a nuclear complex and to play a major role in endosperml development and fertilization (Ohad, N. et al. (1999) Plant Cell 11:407-416). Polycomb-group genes have not been previously described in monocots.
The instant invention relates to isolated nucleic acid fragments encoding factors involved in regulation of gene expression. Specifically, this invention concerns an isolated nucleic acid fragment encoding an anti-silencing protein or a polycomb-group protein. In addition, this invention relates to a nucleic acid fragment that is complementary to the nucleic acid fragment encoding an anti-silencing protein or a polycomb-group protein.
An additional embodiment of the instant invention pertains to a polypeptide encoding all or a substantial portion of a factor involved in regulation of transcription or gene expression selected from the group consisting of anti-silencing proteins and polycomb-group proteins.
In another embodiment, the instant invention relates to a chimeric gene encoding an anti-silencing protein or a polycomb-group protein, or to a chimeric gene that comprises a nucleic acid fragment that is complementary to a nucleic acid fragment encoding an anti-silencing protein or a polycomb-group protein, operably linked to suitable regulatory sequences, wherein expression of the chimeric gene results in production of levels of the encoded protein in a transformed host cell that is altered (i.e., increased or decreased) from the level produced in an untransformed host cell.
In a further embodiment, the instant invention concerns a transformed host cell comprising in its genome a chimeric gene encoding an anti-silencing protein or a polycomb-group protein, operably linked to suitable regulatory sequences. Expression of the chimeric gene results in production of altered levels of the encoded protein in the transformed host cell. The transformed host cell can be of eukaryotic or prokaryotic origin, and include cells derived from higher plants and microorganisms. The invention also includes transformed plants that arise from transformed host cells of higher plants, and seeds derived from such transformed plants.
An additional embodiment of the instant invention concerns a method of altering the level of expression of an anti-silencing protein or a polycomb-group protein in a transformed host cell comprising: a) transforming a host cell with a chimeric gene comprising a nucleic acid fragment encoding an anti-silencing protein or a polycomb-group protein; and b) growing the transformed host cell under conditions that are suitable for expression of the chimeric gene wherein expression of the chimeric gene results in production of altered levels of an anti-silencing protein or a polycomb-group protein in the transformed host cell.
An addition embodiment of the instant invention concerns a method for obtaining a nucleic acid fragment encoding all or a substantial portion of an amino acid sequence encoding an anti-silencing protein or a polycomb-group protein.